排序方式: 共有145条查询结果,搜索用时 734 毫秒
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Songlin Li Lei Wang Yuming Xiong Gyuyeol Bae Changhee Lee 《Journal of Materials Engineering and Performance》2013,22(12):3717-3722
The coating formation in a kinetic spray process mainly depends on the impact of inflight particles at a high velocity. The plastic deformation at the impact interface would disrupt the native oxide scale on the particle and the substrate to generate the intimate contact of the atomic structures. Accordingly, it poses a challenge in producing ceramic coating during kinetic spray because of the lack of plasticity of ceramic powders at room temperature. In this study, we proposed to prepare ZrO2 ceramic coatings using partially amorphized powder with nanometer size in the kinetic spray process. To prepare the powder for the use of the kinetic spray, the amorphization and grain refinement of ZrO2 powder in mechanical ball milling were studied. The results showed that the amorphization and grain refinement were improved because of the formation of solid solution when the CeO2 agent was added. Subsequently, a nearly spherical powder was achieved via spray drying using the milled powders. The plasticity of the milled powders was tested in the kinetic spray process using Nitrogen as process gas. A dense ZrO2-CeO2 coating with a thickness of 50 μm was formed, whereas spraying milled ZrO2 powder can only lead to an inhomogeneous dispersion of the destructible particles on the surface of the substrate. 相似文献
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The vacuum kinetic spray (VKS) process, also-called aerosol deposition, is a promising spray technology by which a thin or thick film can be fabricated at room temperature. Although a number of relevant studies have been performed, almost all have focused on the development of various applications, and unfortunately, the deposition mechanism has not yet been clarified. In this respect, the particle velocity in the flow field in VKS is investigated as a first stage of research into the VKS deposition mechanism. In this research, after a simulation prototype was derived based on the experimental results, the particle average and impact velocities were estimated. In addition, the change in particle velocities with gas flow rates, particle size, and working distance was analyzed based on simulation analyses and microstructural evidence. As a result, the gas flow rate, particle size, and working distance affect the particle impact velocity and further deposition behavior and film microstructure. 相似文献
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Sanghoon Kim Sangchul Lee Kyutae Han Seunggab Hong Changhee Lee 《Metals and Materials International》2010,16(3):483-488
In this work, the microstructural evolution and cracking behavior of a dissimilar weld between high silicon nodular cast iron
and ferritic stainless steel was investigated. An austenitic filler metal (Y309) was employed to produce the dissimilar weld.
Microstructural analysis revealed that cracking formed at the unmixed zone (UMZ) and propagated into the partially melted
zone (PMZ) in the bond line between the cast iron and the Y309, with hard layers formed around the bond line. The cracking
behavior was strongly related to the difference in the melting points of cast iron and the Y309 filler metal, the local liquation
of the laves phase, and the constitutional liquation between the graphite and austenite phases in the PMZ. 相似文献
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Yongjoon Kang Kyutae Han Joo Hyun Park Changhee Lee 《Metallurgical and Materials Transactions A》2014,45(11):4753-4757
The mechanism of formation of an Mn-depleted zone (MDZ) near the inclusion in a steel weld was elucidated based on quantification of MDZ depth and thermodynamic calculations. The effective inclusion phase for intragranular nucleation, which increased as a function of increasing chemical driving force, satisfied the requirements for presence of a considerable quantity of Mn in the phase, and a lower precipitation temperature compared with the solidus temperature of the matrix. 相似文献
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Bright and efficient full-color colloidal quantum dot light-emitting diodes using an inverted device structure 总被引:2,自引:0,他引:2
Kwak J Bae WK Lee D Park I Lim J Park M Cho H Woo H Yoon do Y Char K Lee S Lee C 《Nano letters》2012,12(5):2362-2366
We report highly bright and efficient inverted structure quantum dot (QD) based light-emitting diodes (QLEDs) by using solution-processed ZnO nanoparticles as the electron injection/transport layer and by optimizing energy levels with the organic hole transport layer. We have successfully demonstrated highly bright red, green, and blue QLEDs showing maximum luminances up to 23,040, 218,800, and 2250 cd/m(2), and external quantum efficiencies of 7.3, 5.8, and 1.7%, respectively. It is also noticeable that they showed turn-on voltages as low as the bandgap energy of each QD and long operational lifetime, mainly attributed to the direct exciton recombination within QDs through the inverted device structure. These results signify a remarkable progress in QLEDs and offer a practicable platform for the realization of QD-based full-color displays and lightings. 相似文献
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The performance effect of organic solar cells with subphthalocyanine (SubPC)/fullerene (C60) bilayer was investigated with thermal treatment while changing the vacuum deposition rate of SubPC. The thermal annealing at 100 degrees C increases the optical absorption intensity of SubPC film at the spectral range of 550-630 nm. The X-ray diffraction (XRD) patterns indicates that the thermally annealed film formed the much-ordered morphology, as compared to the non-annealed film. Consequently, thermally treated solar cell exhibited almost 10% higher power conversion efficiency (PCE) compared to the non-annealed device. The fill factor (FF) and PCE of the devices were increased as the deposition rate of SubPC was increased up to 5 A/s and then saturated at higher deposition rates (> 5 A/s). The surface roughness of SubPC films, measured with an atomic force microscope, increased from 1.1 to 5 nm as the deposition rate increased from 1 to 7 A/s. These results imply that rough surface increases the interfacial area between SubPC and C60 and thereby improves the separation of photogenerated electron and hole pairs at the SubPC/C60 interface. 相似文献
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Kicheol Kang Sanghoon Yoon Youlgwun Ji Changhee Lee 《Materials Science and Engineering: A》2008,486(1-2):300-307
In kinetic spraying process, critical velocity is an important criterion which determines the deposition of feedstock onto the substrate. It has been proven experimentally and numerically that the critical velocity is determined by physical and mechanical properties and the state of materials such as initial temperature and size. In this study, the oxidation effect on critical velocity was investigated using experimental methods. As oxygen content of feedstock increased, critical velocity significantly decreased. In order to find out reasons for difference in critical velocity with oxygen content, individual impact behavior was analyzed and interface microstructure was observed. Due to high brittleness and hardness of oxide, oxide layer on particle influences the particle deformation behavior during impact. And oxide accumulated at interface obstructs the adhesion between activated particle and substrate surface during impact. 相似文献